1. Field of the Invention
The present invention relates to an image displaying apparatus utilizing an electron beam such as a field emission display (FED) and a cathode-ray tube (CRT).
2. Related Background Art
So far, image displaying apparatuses such as CRT's have always been required to have further larger screens, and research therefor is lively being performed. Moreover, as the screens become larger, it becomes an important problem to make the apparatuses thinner in thickness, lighter in weight, and lower in costs. However, because a CRT deflects electrons accelerated by a high voltage with the deflection electrode thereof to excite the phosphor on the face plate thereof, it becomes necessary to lengthen the depth thereof in principle, and then it becomes difficult to provide a CRT thin in thickness and light in weight. The present inventor has researched in respect of a surface conduction electron-emitting device and an image displaying apparatus using the surface conduction electron-emitting device as an image displaying apparatus capable of resolving such a problem.
For example, the inventor has tried to apply a multi-electron beam, source by an electric wiring method shown in FIG. 11 to an image displaying apparatus. That is, the inventor has tried to compose an image displaying apparatus by using a multi-electron beam source in which many surface conduction electron-emitting devices are arranged two-dimensionally and the arranged surface conduction electron-emitting devices are wired in a passive matrix as shown in FIG. 11. In FIG. 11, a reference numeral 4001 designates a surface conduction electron-emitting device shown mimetically, a reference numeral 4002 designates a piece of wiring in a row direction; and a reference numerals 4003 designates a piece of wiring in a column direction. Incidentally, although a six by six matrix is shown in FIG. 11 on account of the convenience of description, the scale of the matrix is not limited to the six by six one and devices necessary for displaying a desired image can be arranged.
FIG. 12 shows the structure of a cathode-ray tube using the multi-electron beam source. The structure comprises an outer housing bottom 4005 including a multi-electron beam source 4004, an outer housing frame 4007, and a face plate 4006 including a phosphor layer 4008 and a metal-backing 4009. Moreover, the phosphor layer 4008 on the face plate 4006 includes phosphor thereby excited by an electron beam to emit light, and a black matrix for suppressing the reflection of outer light to prevent color mixture in the phosphor. A high electric potential Va is applied to the phosphor layer 4008 and the metal-backing 4009 through a high voltage terminal 4011, and the phosphor layer 4008 and the metal-backing 4009 constitutes an anode.
For the outputting of a desired electron beam from the multi-electron beam source 4004 in which surface conduction electron-emitting devices 4001 are wired in a passive matrix, appropriate electric signals are applied to the pieces of wiring 4002 in row directions and the pieces of wiring 4003 in column directions of the multi-electron beam source 4004. For example, for the drive of the surface conduction electron-emitting devices 4001 in an arbitrary row of the matrix, a selection potential Vs is applied to the wiring 4002 in the row direction to be selected, and at the same time a nonselection potential Vns is applied to the wiring 4002 in the row directions not to be selected. Synchronously to this, a drive potential Ve for outputting electron beams is applied to the pieces of the wiring 4003 in the column directions.
By this method, the voltages Ve and Vs are applied to the surface conduction electron-emitting devices 4001 of the rows to be selected, and the voltages Ve and Vns are applied to the surface conduction electron-emitting devices 4001 of the rows not to be selected. By the settings of the voltages Ve, Vs and Vns to be appropriate potentials, electron beams having desired strength can be outputted only from the surface conduction electron-emitting devices 4001 of the rows to be selected. And, when drive potentials Ve having different strength from each other are applied to each of the wiring 4003 in the column directions, electron beams having different strength are outputted from each surface conduction electron-emitting devices 4001 in the row to be selected. Moreover, because the response speed of the surface conduction electron-emitting devices 4001 is high, the length of time during which electron beams are outputted can also be changed by the change of the length of time during which the drive potential Ve is applied.
By the application of such electric potentials, the electron beams outputted from the multi-electron beam source 4004 irradiate the metal-backing 4009, which the high electric potential Va is applied to, and excite the phosphor, or the target, to make the phosphor emit light. Moreover, in the image displaying apparatus, the high electric potential Va (sometimes referred to as an “accelerating potential” or an “anode potential”) is applied to the metal-backing 4009 to generate an electric field between the outer housing bottom 4005 (sometimes referred to as a “rear plate”) and the face plate 4006. Thereby, electrons emitted from the multi-electron beam source 4004 are accelerated and excite the phosphor to emit light. Consequently, an image is formed.
Now, because the brightness of an image displaying apparatus depends on an accelerating potential greatly, it is necessary to heighten the accelerating potential for the realization of high brightness. Moreover, because the thickness of an image displaying panel should be thinned for the realization of the thinning of the image displaying apparatus, the distance between the rear plate 4005 and the face plate 4006 should be shorten therefor. Consequently, a considerably high electric field is generated between the rear plate 4005 and the face plate 4006.